The problem is the vast majority of tanks you’ll meet are people who don’t actually do any tanking outside of that specific dungeon run, guilds only need 2-3 tanks after all. M+ fixed this a bit, but it’s still probably mostly true, especially outside of M+ which is what people are doing now.
It’s not really a “tank ego” problem, so much as it is a “DPS playing tank with an ego” problem. And they’re usually DPS who don’t really play healers, so they can’t empathize with what it’s like for you at all.